Browsing by Author "Park, Yujin"

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    A Multimodal Educational Boot Camp for Training Fellows in Pediatric Extracorporeal Membrane Oxygenation (ECMO)
    (Association of American Medical Colleges, 2024-10-17) Park, Yujin; Hocutt, Gail; Wetzel, Elizabeth; Swinger, Nathan; Pearson, Kellie; Abulebda, Kamal; Gray, Brian; Surgery, School of Medicine
    Introduction: Pediatric extracorporeal membrane oxygenation (ECMO) management presents unique challenges in acute care settings, requiring specialized expertise to manage critically ill children. Medical and surgical fellows often manage these patients, but prior residency training rarely provides sufficient ECMO exposure. We developed and evaluated a multimodal pediatric ECMO boot camp for new fellows. Methods: This boot camp was implemented during 5-hour sessions in August 2021, August 2022, and August 2023. The curriculum included a 45-minute introductory didactics session, 30-minute hands-on circuit demonstration, and four 30-minute small-group activity stations. To assess knowledge acquisition, pre- and posttests were administered; participants also completed a post-boot camp survey to evaluate their confidence and provide feedback. Results: Forty-nine participants completed the boot camp, including 18 critical care, four cardiology, 11 pediatric surgery, 12 cardiothoracic surgery, and four pediatric emergency medicine fellows. Pre- and posttests demonstrated significant improvement in knowledge of ECMO circuit components and pressures (56% vs. 76%, p < .001). All of our participants agreed or strongly agreed that participating in the boot camp increased their confidence in troubleshooting ECMO emergencies. The inclusion of fellows from various clinical disciplines, offering a rich diversity of perspectives, was particularly valued by participants. Discussion: Our results demonstrate the feasibility and effectiveness of establishing a pediatric ECMO boot camp to train new surgical and medical fellows. The curriculum not only improved ECMO knowledge but also boosted learners' confidence in managing ECMO-related challenges.
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    Co-expression of HLA-E and HLA-G on genetically modified porcine endothelial cells attenuates human NK cell-mediated degranulation
    (Frontiers Media, 2023-07-17) Cross-Najafi, Arthur A.; Farag, Kristine; Isidan, Abdulkadir; Li, Wei; Zhang, Wenjun; Lin, Zhansong; Walsh, Julia R.; Lopez, Kevin; Park, Yujin; Higgins, Nancy G.; Cooper, David K. C.; Ekser, Burcin; Li, Ping; Surgery, School of Medicine
    Natural killer (NK) cells play an important role in immune rejection in solid organ transplantation. To mitigate human NK cell activation in xenotransplantation, introducing inhibitory ligands on xenografts via genetic engineering of pigs may protect the graft from human NK cell-mediated cytotoxicity and ultimately improve xenograft survival. In this study, non-classical HLA class I molecules HLA-E and HLA-G were introduced in an immortalized porcine liver endothelial cell line with disruption of five genes (GGTA1, CMAH, β4galNT2, SLA-I α chain, and β-2 microglobulin) encoding three major carbohydrate xenoantigens (αGal, Neu5Gc, and Sda) and swine leukocyte antigen class I (SLA-I) molecules. Expression of HLA-E and/or HLA-G on pig cells were confirmed by flow cytometry. Endogenous HLA-G molecules as well as exogenous HLA-G VL9 peptide could dramatically enhance HLA-E expression on transfected pig cells. We found that co-expression of HLA-E and HLA-G on porcine cells led to a significant reduction in human NK cell activation compared to the cells expressing HLA-E or HLA-G alone and the parental cell line. NK cell activation was assessed by analysis of CD107a expression in CD3-CD56+ population gated from human peripheral blood mononuclear cells. CD107a is a sensitive marker of NK cell activation and correlates with NK cell degranulation and cytotoxicity. HLA-E and/or HLA-G on pig cells did not show reactivity to human sera IgG and IgM antibodies. This in vitro study demonstrated that co-expression of HLA-E and HLA-G on genetically modified porcine endothelial cells provided a superior inhibition in human xenoreactive NK cells, which may guide further genetic engineering of pigs to prevent human NK cell mediated rejection.
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    Current Barriers to Clinical Liver Xenotransplantation
    (Frontiers Media, 2022-02-23) Cross-Najafi, Arthur A.; Lopez, Kevin; Isidan, Abdulkadir; Park, Yujin; Zhang, Wenjun; Li, Ping; Yilmaz, Sezai; Akbulut, Sami; Ekser, Burcin; Surgery, School of Medicine
    Preclinical trials of pig-to-nonhuman primate liver xenotransplantation have recently achieved longer survival times. However, life-threatening thrombocytopenia and coagulation dysregulation continue to limit preclinical liver xenograft survival times to less than one month despite various genetic modifications in pigs and intensive pharmacological support. Transfusion of human coagulation factors and complex immunosuppressive regimens have resulted in substantial improvements in recipient survival. The fundamental biological mechanisms of thrombocytopenia and coagulation dysregulation remain incompletely understood. Current studies demonstrate that porcine von Willebrand Factor binds more tightly to human platelet GPIb receptors due to increased O-linked glycosylation, resulting in increased human platelet activation. Porcine liver sinusoidal endothelial cells and Kupffer cells phagocytose human platelets in an asialoglycoprotein receptor 1-dependent and CD40/CD154-dependent manner, respectively. Porcine Kupffer cells phagocytose human platelets via a species-incompatible SIRPα/CD47 axis. Key drivers of coagulation dysregulation include constitutive activation of the extrinsic clotting cascade due to failure of porcine tissue factor pathway inhibitor to repress recipient tissue factor. Additionally, porcine thrombomodulin fails to activate human protein C when bound by human thrombin, leading to a hypercoagulable state. Combined genetic modification of these key genes may mitigate liver xenotransplantation-induced thrombocytopenia and coagulation dysregulation, leading to greater recipient survival in pig-to-nonhuman primate liver xenotransplantation and, potentially, the first pig-to-human clinical trial.
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    Development and Characterization of Human Primary Cholangiocarcinoma Cell Lines
    (Elsevier, 2022) Isidan, Abdulkadir; Yenigun, Ali; Soma, Daiki; Aksu, Eric; Lopez, Kevin; Park, Yujin; Cross-Najafi, Arthur; Li, Ping; Kundu, Debjyoti; House, Michael G.; Chakraborty, Sanjukta; Glaser, Shannon; Kennedy, Lindsey; Francis, Heather; Zhang, Wenjun; Alpini, Gianfranco; Ekser, Burcin; Medicine, School of Medicine
    Cholangiocarcinoma (CCA) is the second most common primary liver tumor and is associated with late diagnosis, limited treatment options, and a 5-year survival rate of around 30%. CCA cell lines were first established in 1971, and since then, only 70 to 80 CCA cell lines have been established. These cell lines have been essential in basic and translational research to understand and identify novel mechanistic pathways, biomarkers, and disease-specific genes. Each CCA cell line has unique characteristics, reflecting a specific genotype, sex-related properties, and patient-related signatures, making them scientifically and commercially valuable. CCA cell lines are crucial in the use of novel technologies, such as three-dimensional organoid models, which help to model the tumor microenvironment and cell-to-cell crosstalk between tumor-neighboring cells. This review highlights crucial information on CCA cell lines, including: i) type of CCA (eg, intra- or extrahepatic), ii) isolation source (eg, primary tumor or xenograft), iii) chemical digestion method (eg, trypsin or collagenase), iv) cell-sorting method (colony isolation or removal of fibroblasts), v) maintenance-medium choice (eg, RPMI or Dulbecco's modified Eagle's medium), vi) cell morphology (eg, spindle or polygonal shape), and vii) doubling time of cells.
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    Liver Transplantation in Recipients With Class III Obesity: Posttransplant Outcomes and Weight Gain
    (Wolters Kluwer, 2022-01-05) Soma, Daiki; Park, Yujin; Mihaylov, Plamen; Ekser, Burcin; Ghabril, Marwan; Lacerda, Marco; Chalasani, Naga; Mangus, Richard S.; Kubal, Chandrashekhar A.; Surgery, School of Medicine
    Background: There has been a dramatic increase in obesity in the United States. Several studies have reported conflicting results for the impact of obesity on outcomes of liver transplantation (LT). This study aims to assess the impact of obesity on LT and changes in body mass index (BMI) after transplantation. Methods: All adult LTs performed at Indiana University between 2001 and 2018 were reviewed. BMIs of recipients were subdivided into 6 categories. Survival outcomes were compared across the subgroup. BMI was followed up in a cohort of patients from 2008 to 2018. Results: Among 2024 patients, 25% were in class I obesity, 9.3% were in class II obesity, and 1.1% were in class III obesity. There was no significant difference in patient and graft survival at 10-y follow-up with respect to BMI. Among 1004 patients in the subgroup, BMI of all groups except the underweight group declined in the first 3 mo postoperatively; however, the BMI of all groups except the class III obesity group returned to the pre-LT level by 2 y and reached a plateau by 5 y. In the class III obesity group, there was a significant increase in body weight at 5 y. Conclusions: Class III obesity was not associated with higher mortality in our cohort. Because our cohort is small, it may be underpowered to detect a smaller difference in outcome. From our observation, obesity should not be considered a contraindication for LT. Post-LT interventions are required to prevent significant weight gain for the class III obesity group.
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    Strategies to induce natural killer cell tolerance in xenotransplantation
    (Frontiers Media, 2022-08-22) Lopez, Kevin J.; Cross-Najafi, Arthur A.; Farag, Kristine; Obando, Benjamin; Thadasina, Deepthi; Isidan, Abdulkadir; Park, Yujin; Zhang, Wenjun; Ekser, Burcin; Li, Ping; Surgery, School of Medicine
    Eliminating major xenoantigens in pig cells has drastically reduced human antibody-mediated hyperacute xenograft rejection (HXR). Despite these advancements, acute xenograft rejection (AXR) remains one of the major obstacles to clinical xenotransplantation, mediated by innate immune cells, including macrophages, neutrophils, and natural killer (NK) cells. NK cells play an ‘effector’ role by releasing cytotoxicity granules against xenogeneic cells and an ‘affecter’ role on other immune cells through cytokine secretion. We highlight the key receptor-ligand interactions that determine the NK cell response to target cells, focusing on the regulation of NK cell activating receptor (NKG2D, DNAM1) and inhibitory receptor (KIR2DL1-4, NKG2A, and LIR-1) signaling pathways. Inhibition of NK cell activity may protect xenografts from cytotoxicity. Recent successful approaches to reducing NK cell-mediated HXR and AXR are reviewed, including genetic modifications of porcine xenografts aimed at improving pig-to-human compatibility. Future directions to promote xenograft acceptance are discussed, including NK cell tolerance in pregnancy and NK cell evasion in viral infection.
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    Three-Dimensional Organoids as a Model to Study Nonalcoholic Fatty Liver Disease
    (Thieme, 2022) Park, Yujin; Thadasina, Deepthi; Bolujo, Ifeoluwa; Isidan, Abdulkadir; Cross-Najafi, Arthur A.; Lopez, Kevin; Li, Ping; Dahlem, Andrew M.; Kennedy, Lindsey; Sato, Keisaku; Francis, Heather; Alpini, Gianfranco; Zhang, Wenjun; Ekser, Burcin; Surgery, School of Medicine
    Despite the rising prevalence of nonalcoholic fatty liver disease (NAFLD), the underlying disease pathophysiology remains unclear. There is a great need for an efficient and reliable "human" in vitro model to study NAFLD and the progression to nonalcoholic steatohepatitis (NASH), which will soon become the leading indication for liver transplantation. Here, we review the recent developments in the use of three-dimensional (3D) liver organoids as a model to study NAFLD and NASH pathophysiology and possible treatments. Various techniques that are currently used to make liver organoids are discussed, such as the use of induced pluripotent stem cells versus primary cell lines and human versus murine cells. Moreover, methods for inducing lipid droplet accumulation and fibrosis to model NAFLD are explored. Finally, the limitations specific to the 3D organoid model for NAFLD/NASH are reviewed, highlighting the need for further development of multilineage models to include hepatic nonparenchymal cells and immune cells. The ultimate goal is to be able to accurately recapitulate the complex liver microenvironment in which NAFLD develops and progresses to NASH.